mark synthesized protected member as notPROTECTED,

TODO: this doesn't work because protected[this] is supposed to be a
variance checking escape hatch, and making these notPROTECTED here will trigger errors in refchecks

so that it stays in overriding relation with the trait member in later phases

make notPROTECTED a bit later?

protected local variance bla

Author: adriaanm

src/compiler/scala/tools/nsc/transform/Fields.scala

@@ -128,9 +128,17 @@ abstract class Fields extends InfoTransform with ast.TreeDSL with TypingTransfor
             // required for private vals in traits
             accessor.makeNotPrivate(clazz)
 
+            // Need to mark as notPROTECTED, so that it's carried over to the synthesized member in subclasses,
+            // since the trait member will receive this flag later in ExplicitOuter, but the synthetic subclass member will not.
+            // If we don't add notPROTECTED to the synthesized one, the member will not be seen as overriding the trait member.
+            // Therefore, addForwarders's call to membersBasedOnFlags would see the deferred member in the trait,
+            // instead of the concrete (desired) one in the class
+            if (accessor.isProtected) accessor setFlag notPROTECTED
+
             // trait members cannot be final (but the synthesized ones should be)
-            // LOCAL no longer applies (already made not-private)
-            accessor resetFlag (FINAL | LOCAL)
+            // must not reset LOCAL, as we must maintain protected[this]ness to allow that variance hole
+            // (not sure why this only problem only arose when we started setting the notPROTECTED flag)
+            accessor resetFlag (FINAL)
 
             // derive trait setter after calling makeNotPrivate (so that names are mangled consistently)
             if (memoizedGetter) {

test/files/trait-defaults/static_fwd.scala

@@ -0,0 +1,10 @@
+trait T {
+  // Need to mark the synthesized member in the object's module class as notPROTECTED,
+  // since the trait member will receive this flag later.
+  // If we don't add notPROTECTED to the synthesized one, the member will not be seen as overriding the trait member.
+  // Therefore, addForwarders's call to membersBasedOnFlags would see the deferred member in the trait,
+  // instead of the concrete (desired) one in the class, and thus not create the static forwarder.
+  protected val propFilename: String = "/"
+}
+
+object P extends T